Currently, a distributed base station is widely applied in a live network. A characteristic of the distributed base station is that a radio equipment (RE) is separated from a radio equipment control (REC), and then the two are connected using an optical fiber.
During network deployment, RECs may be deployed in a centralized manner in an equipment room to form a baseband pool, and then the RECs are connected, using optical fibers, to REs deployed on a planned site, to complete network coverage. A common public radio interface (CPRI) may be used to connect an REC to an RE, and an RE to an RE.
Generally, the CPRI has strict clock synchronization requirement and time synchronization requirement. The clock synchronization requirement may be understood as that an offset between a frequency at which an REC sends a CPRI service frame and a frequency at which an RE sends a CPRI service frame should be controlled within a particular range such that accuracy of an air interface frequency is ensured. The time synchronization requirement may be understood as that a communication delay between an REC and an RE remains unchanged.
To meet the time synchronization requirement, a communication delay between the REC and the RE may be calculated, and based on the communication delay, in a downlink direction, a downlink signal sending moment of the REC is controlled, and in an uplink direction, an uplink signal transmission delay of the RE is compensated for such that the communication delay between the REC and the RE is ensured to remain unchanged. Referring to FIG. 1, a communication delay Tcommunication=Ta+Tb+Tc+Td, where Ta is a delay between a time when an REC stamps a sending time stamp and a time when the REC sends a sampling signal, Tb is a transmission delay of the sampling signal on an optical fiber link, Tc is a delay between a time when an RE receives the sampling signal and a time when the RE stamps a receiving time stamp, and Td is a delay between the time when the RE stamps the receiving time stamp and a time when the sampling signal is transmitted to a delay test reference point. For example, a signal transmit point, that is, an antenna port, of the RE is defined as the delay test reference point.